The present invention relates to a touch panel (or a touch sensor or touch screen) to input/output coordinate information on touch-positions touched with fingers or the like, and more particularly to a touch panel (or a touch-position detecting device) having transmitting and receiving elements to utilize acoustic wave (e.g. surface ultrasonic wave).
As primary type of the touch panels, there have been known the surface ultrasonic wave type, the resistance film type, the electrostatic capacity type, the electromagnetic induction type and others. Among these types, the surface ultrasonic wave type includes one known method in which transmitting and receiving transducers are placed opposite each other in both directions of X and Y axes of the surface of a propagation medium, such as a glass substrate, to detect the touch-positions.
On the other hand, as a widely popularized method in recent years, there has been known a method in which respective pairs of transmitting and receiving transducers (four transducers in total) for detecting respective X and Y coordinates or coordinate values are placed in a propagation medium through an array of reflective elements to detect the touch-positions (U.S. Pat. No. 4,746,914, U.S. Reissue Pat. No. 33151 and International Patent Laid-Open Publication WO 96/23292). In this method, a wend face type transducer is used to simultaneously switch over a transmitting circuit and receiving circuit of an electric signal processing circuit (controller) in order to process respective signals of X and Y axes. Using such a signal processing leads to two partially or entirely duplicate groups not only of the switching circuit but also of the transmitting and receiving circuits in the controller, which results in complicated circuit structure and signal processing as well as increased cost.
Further, when the aforementioned transducer is mounted on the surface of the propagation medium, a raised portion is formed on the surface of the propagation medium. This makes difficult to arrange a liquid crystal display apparatus (LCD), particularly a thin LCD monitor to the propagation medium.
Thus, it is an object of the present invention to provide a touch panel or touch-position detecting device capable of preventing from forming raised portions on the surface of the propagation medium to enhance applicability to the thin LCD monitor and to simplify its structure.
It is another object of the present invention to provide a touch panel capable of reducing the number of transducers and simplifying circuit structure and signal processing.
The inventors of the present invention noted the fact that a small gap was essentially caused between the rear surface of a propagation medium (panel) and a display apparatus. As a result of their sedulous studies for achieving the aforementioned object, they have found out that when the end face or corner portion of the propagation medium allowing acoustic wave (surface ultrasonic wave) to be propagated was chamfered or rounded, the acoustic wave could turn around and be propagated from the front surface to the rear surface of the propagation medium, or from the rear surface to the front surface of the propagation medium, through the chamfered portion (rounded portion or propagation-direction changing portion), and the present invention eventually has been completed.
Specifically, a touch panel (touch-position detecting device) according to the present invention comprises a medium allowing acoustic wave to be propagated and a transducer, mounted on this propagation medium, for transmitting and receiving the acoustic wave, wherein the end face or the corner portion of the propagation medium is chamfered. In such a touch panel, the acoustic wave may be propagated bidirectionally between the front and rear surfaces of the acoustic wave propagation medium through the chamfered portion (propagation-direction changing portion). Thus, the transducer may be mounted on the front surface and/or rear surface of the acoustic wave propagation medium. In the touch panel, the corner portion of at least one of the front and rear surfaces of the acoustic wave propagation medium and the side surface of the acoustic wave propagation medium (i.e. an edge at which the front or rear surface of the propagation medium intersects the side surface thereof) is chamfered, and then a transducer may be mounted on the side surface of the propagation medium.
Further, when the end face is chamfered, the acoustic wave may be propagated in the reverse direction (i.e. from an X-axis direction to a negative (xe2x88x92) X-axis direction) through the chamfered portion (direction changing portions), and otherwise, when the corner portion is chamfered, the acoustic wave may be directionally changed from the X-axis direction to a Y-axis direction through the chamfered portion (direction changing portions).
Furthermore, when a V-shaped (or valley-shaped) cut portion or an chevron-shaped raised portion is formed and this cut or raised portion (direction changing portion) is chamfered, the acoustic wave propagated from the X-axis and Y-axis directions on one surface of the propagation medium may turn around and converge through the chamfered portion (direction changing portions). In other words, when the acoustic wave are transmitted from a convergent portion on another surface of the propagation medium, the acoustic wave on the one surface of the propagation medium may be propagated with making it branch into the X-axis and Y-axis directions. Thus, the transducer may be mounted at the aforementioned convergent area or branch area, and this allows a single transducer to transmit and receive the acoustic wave in the X-axis and Y-axis directions.
Utilizing such a chamfered portion (direction changing portion) allows the acoustic wave to be propagated from one surface to the other surface of the propagation medium, so that at least one transducer may be mounted on the rear surface of the propagation medium. For example, the transmitting and receiving transducers may be made up of two or three transducers.
The radius (R) of the aforementioned chamfered portion is typically 0.5 mm or more.
The present invention also includes a touch-position detecting device comprising a medium which allows acoustic wave to be propagated in the X-axis and Y-axis directions thereof, at least one transmitting transducer, mounted on the propagation medium, for generating the acoustic wave in the X-axis and Y-axis directions, a chamfered portion (direction changing portion), formed at the end face and/or corner portion of the propagation medium, for making the acoustic wave from the transmitting transducer being propagated from the front or rear surface to the rear or front surface of the propagation medium, and at least one receiving transducer, mounted on the propagation medium, for detecting a touch-position of the X-axis and Y-axis coordinates by use of the acoustic wave which has turned around and been propagated through the chamfered portion.
Such a touch panel utilizes a characteristic that acoustic wave (e.g. surface ultrasonic wave or the like) is propagated straight on the surface of a propagation medium. Specifically, when the acoustic wave turns around the end face of the panel, it spirally travels on the surface having semicircular shape in section. Thus, the acoustic wave generated on the rear surface of the touch panel turns around the end face of the panel and is then guided to the front surface as a touch surface. When the acoustic wave are propagated on the surface of the propagation medium, the traveling direction of the acoustic wave may be easily understood by referring a development view for the propagation medium which is a hollow and made up only of a shell. For example, as shown in FIG. 1, the traveling direction (see the arrow) of the acoustic wave traveling on the spherical surface of a sphere 1 corresponds to the outline of a section made by cutting the sphere along a plane including the center of the sphere 1. As shown in FIG. 2, when acoustic wave travels on the surface of a columnar propagation medium 2, it spirally travels on the surface of the propagation medium as shown by the arrow. Thus, when the end face or corner portion of the propagation medium is chamfered and processed into a gentle surface (curved surface), the acoustic wave are directed from one of the front and rear surfaces of the propagation medium to another surface practically without any loss.
The term xe2x80x9csurfacexe2x80x9d herein refers to the vicinity of the surface of a propagation medium or the surface layer of the propagation medium, on which acoustic wave is propagated.